I am completely anti-fannypack in my everyday life, but it's my favorite way to tote all my junk at the parks. I get hot very easily, so a backpack doesn't work for me -- it just leaves my back a sweaty mess

. I also want my hands free to take pictures, point things out, etc. So, the fannypack works best for me.
My fannypack stash includes:
Park Passes/room key
Fast passes
Cash (minimal amount since we usually charge everything to the room)
ID
Small tube of sunblock
Camera
Purell (hand sanitizer -- public bathroom sinks gross me out)
Digital camera
Park map (more for souvenier purposes than because I really need it anymore

)
Gum/mints
Anything else is too much to lug around.